[processor/deltatocumulative]: progress tracking

[sh0rez]

Important

This is strictly for progress tracking. Please do any discussion in #30479

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• Structure PR: [processor/deltatocumulative]: initial structure #30706
• Design proposal: new component: deltatocumulative processor #30479
• Implementation
  • Accumulate Sums: [processor/deltatocumulative]: Sums #30707
    • [processor/deltatocumulative]: bugfix - permit advancing start-time #31365
    • [processor/deltatocumulative]: bugfix - process all samples #31349
  • Accumulate Histograms: [processor/deltatocumulative]: explicit-bounds histograms #33983
  • Accumulate exp. Histograms:
    • discuss: exponential histogram addition #31340
    • deltatocumulative: exponential histograms #32030
  • Purge stale series:
    • discuss: stateful series tracking staleness #31016
    • [processor/deltatocumulative]: expire stale series #31337
    • [processor/deltatocumulative]: timer-based expiry #31625
  • Series Limit
    • [processor/deltatocumulative] limit tracked streams #31488
    • [processor/deltatocumulative]: determine default stream limit #31603
  • Handle out of order samples:
    • [processor/deltatocumulative]: reorder incoming samples #32958
  • Instrumentation:
    • [processor/deltatocumulative]: observe accumulation metrics #31363
    • Propagate request context.Context from ConsumeMetrics()
  • Lifecycle tests: TODO
• Future
  • Analyze if global locking is a bottleneck, if so choose a more efficient data structure / sync strategy
  • Investigate horizontal scaling options, similar to loadbalancingexporter